Fluid controller

ABSTRACT

A fluid control device  1  has an upper space S 1  formed between and defined by the upper surface of a piston  10  and the lower surface of top wall  8   a  of an upper casing  8,  and a lower space S 2  formed between and defined by the lower surface of the piston  10  and the upper surface of bottom wall  7   a  of a lower casing  7.  A compression coil spring  11  for biasing the piston  10  is disposed in one of the upper space S 1  and the lower space S 2,  and a compressed air admitting passage  15  communicates with the other space.

TECHNICAL FIELD

The present invention relates to fluid control devices, and moreparticularly to a fluid control device which is of the normally opentype or normally closed type as determined in accordance with thedirection of the biasing force of a spring incorporated therein andwherein a fluid channel is opened or closed by the supply or dischargeof compressed air.

BACKGROUND ART

Normally closed fluid control devices are already known which comprise avalve case having a fluid channel, a valve element holder upwardly ordownwardly movable for holding a valve element for opening or closingthe fluid channel, a lower casing attached to a bonnet provided on anupper portion of the valve case, an upper casing joined to the lowercasing, a valve stem disposed in a space defined by the upper and lowercasings and having a lower end in bearing contact with the valve elementholder, a piston secured to the valve stem by a retaining ring, and acompression coil spring bearing on and retained by the top wall of thebonnet and a flange provided on the valve stem so as to be positionedbelow the bonnet top wall. The fluid channel is opened by admittingcompressed air into a lower space formed between and defined by thelower surface of the piston and the upper surface of bottom wall of thelower casing (see, for example, the publication of JP-A No. 11-256578,pars. 0002 to 0003 and FIG. 3).

The normally closed fluid control device may be modified into a normallyopen fluid control device by providing a compression coil spring as heldbetween a lower portion of a bonnet and a flange provided on the valvestem so as to be positioned above the bonnet lower portion andintroducing compressed air into an upper space formed between anddefined by the upper surface of the piston and the lower surface of topwall of the upper casing.

With the conventional fluid control devices described above, thenormally closed type and the normally open type are handled as differentindividual devices, such that when designing one of these two types, noconsideration is given to the interior construction of the other type.Accordingly, the control device of the normally open type and that ofthe normally closed type as used on the same piping system are verygreat in the combined number of components.

An object of the present invention is to provide a fluid control devicewhich is useful for providing fluid control devices of the normallyclosed type and the normally open type which are reduced in the combinednumber of components.

DISCLOSURE OF THE INVENTION

The present invention provides a fluid control device comprising a valvecase having a fluid channel, a valve element holder upwardly ordownwardly movable for holding a valve element for opening or closingthe fluid channel, a lower casing provided on an upper portion of thevalve case, an upper casing joined to the lower casing, a valve stemdisposed in a space defined by the upper and lower casings and having alower end in bearing contact with the valve element holder and a pistonsecured to the valve stem, an upper space being formed between anddefined by an upper surface of the piston and a lower surface of a topwall of the upper casing, a lower space being formed between and definedby a lower surface of the piston and an upper surface of a bottom wallof the lower casing, the fluid control device being characterized inthat a compression coil spring is provided in one of the upper space andthe lower space for biasing the piston, a compressed air admittingpassageway being in communication with the other of the upper and lowerspaces.

When the compression coil spring for biasing the piston is provided inthe upper space with the compressed air admitting passageway incommunication with the lower space, the fluid control device of theinvention serves as a fluid control device of the normally closed typewherein the piston is biased downward axially of the device. When thecompression coil spring for biasing the piston is provided in the lowerspace with the compressed air admitting passageway in communication withthe upper space, the fluid control device of the invention serves as afluid control device of the normally open type wherein the piston isbiased upward axially of the device. Accordingly, the normally closedfluid control device and the normally open fluid control device can beobtained by using the valve case, valve element, valve element holder,lower casing, upper casing, valve stem and piston as common components.This reduces the combined number of components of the fluid controldevices of the two types.

The valve stem and the piston may be made separate members and thenconnected together, but it is desirable to provide the valve stem andthe piston in the form of an integral member. This eliminates the needto secure the piston to the valve stem with a retaining ring, decreasingthe number of components and resulting in improved pressure resistance.

Further it is desirable to provide a spring bearing annular recessedportion in each of the top wall lower surface of the upper casing andthe bottom wall upper surface of the lower casing. In the fluid controldevice of the normally closed type, the compression coil spring is thenretained by the annular recessed portion of the top wall of the uppercasing, while in the fluid control device of the normally open type, thecompression coil spring is retained by the annular recessed portion ofthe bottom wall of the lower casing. The coiled spring required for thecontrol device can therefore be retained in place regardless of whetherit is of the normally closed type or normally open type.

Preferably, the top wall of the upper casing is provided with aninternally threaded portion having an upward opening for connecting acompressed air admitting pipe and a compressed air admitting downwardpassage opened to the upper space and extending from a lower end of theinternally threaded portion. The compressed air admitting portion canthen be used in common for the normally closed type and the normallyopen type. For introducing compressed air into the lower space in thenormally closed type, a compressed air passageway is formed in thepiston for causing the downward passage to communicate with the lowerspace.

As a preferred embodiment of fluid control device, the fluid controldevice is of the normally open type, wherein the compression coil springis retained by the lower surface of the piston and the annular recessedportion in the lower casing upper surface. Alternatively the fluidcontrol device is of the normally closed type, wherein a spring bearingannular recessed portion is formed in the upper surface of the piston,and the compression coil spring is retained by the annular recessedportion of the piston and the annular recessed portion in the uppercasing lower surface, the piston having an upper small-diameter portionfitted in the downward passage of the upper casing, the piston beingprovided with a compressed air passageway communicating at an upper endthereof with the downward passage in the top wall of the upper casingand at a lower end thereof with the lower space.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing a first embodiment of fluid controldevice (of the normally open type) according to the invention.

FIG. 2 is a sectional view showing a second embodiment of fluid controldevice (of the normally closed type) according to the invention.

BEST MODE OF CARRYING OUT THE INVENTION

Embodiments of the invention will be descried below with reference tothe drawings. In the following description, the terms “left” and “right”refer respectively to the left- and right-hand sides of the drawings.

FIG. 1 shows a first embodiment of fluid control device of the presentinvention.

The fluid control device 1 of this embodiment is of the normally opentype and comprises a valve case 2 provided with a fluid inlet channel 2a and a fluid outlet channel 2 b, an annular valve seat 3 formed arounda peripheral edge defining an opening of the inlet channel 2 a, adiaphragm (valve element) 4 movable into or out of pressing contact withthe valve seat 3 for closing or opening the fluid channel 2 a, a disk(vale element holder) 5 movable upward or downward for holding thediaphragm 4, a bonnet 6 fitted around the disk 5, a lower casing 7disposed on an upper portion of the valve case 2, an upper casing 8joined to the lower casing 7, a valve stem 9 disposed within a spacedefined by the upper and lower casings 7, 8 and having a lower end inbearing contact with the valve element holder 5, a piston 10 secured tothe valve stem 9, and a compression coil spring 11 for biasing thepiston 10 upward.

The valve case 2 has a cavity 2 c which is open upward. The inletchannel 2 a has one end which is open leftward and the other end whichis open at the center of bottom wall of the cavity 2 c. The outletchannel 2 b has one end which is open rightward and the other end whichis open at a right portion of the bottom wall of the cavity 2 c.

The disk 5 is in the form of a solid cylinder and has a flange 5 a atits lower end. The bonnet 6 is in the form of a hollow cylinder and hasa lower-end inner periphery defining a large-diameter portion 6 a havingan inside diameter slightly larger than the outside diameter of theflange 5 a of the disk 5. The bonnet 6 is tightly fitted in the cavity 2c of the valve case 2 and secures the outer peripheral portion of thediaphragm 4 to the valve case 2. The disk 5 is loosely fitted into thebonnet 6 from below. Although immovable upward in the illustrated state(channel opening state), the disk 5 is movable downward (channel closingdirection).

The lower casing 7 comprises a bottom wall 7 a, a hollow cylindricalperipheral wall 7 b upstanding from the bottom wall 7 a and having anexternally threaded portion on its outer periphery, and a hollowcylindrical downward projection 7 c of small diameter extending downwardfrom the bottom side of the bottom wall 7 a and having an internallythreaded portion on its inner periphery. The internally threaded portionof the downward projection 7 c is in screw-thread engagement with anexternally threaded portion of a peripheral wall of the valve case 2which wall defines the cavity 2 c, whereby the lower casing 7 is securedto the valve case 2. The bonnet 6 is provided on its top with an annularridge 6 b serving as a stopper when the lower casing 7 is tightened up.

An annular recessed portion 12 for retaining the compression coil spring11 is formed in the upper surface of the bottom wall 7 a of the lowercasing 7. A through bore 13 is formed in the bottom wall 7 a of thelower casing 7 centrally thereof for guiding the valve stem 9 upwardlyor downwardly movably.

The upper casing 8 comprises a top wall 8 a and a hollow cylindricalperipheral wall 8 b. The peripheral wall 8 b has an internally threadedportion, which is screwed on the externally threaded portion ofperipheral wall 7 b of the lower casing 7, whereby the upper casing 8and the lower casing 7 are joined to define a space inside thereof. Thetop wall 8 a of the upper casing 8 is provided with an internallythreaded portion 14 formed in the center thereof and having an upwardopening for connecting a compressed air admitting pipe, and a compressedair admitting downward passage 15 extending from the lower end of theinternally threaded portion 14. The top wall 8 a of the upper casing 8has a central portion slightly projecting downward beyond the otherportion thereof and is provided in its lower surface with a springbearing annular recessed portion 16 around this central portion. Thisrecessed portion 16 is used in the normally closed fluid control device21 to be described later.

The valve stem 9 is formed integrally with the piston 10 so as to be aportion projecting downward from the center of the piston 10. The piston10 comprises a large-diameter portion 10 a slidably fitted in the uppercasing 8 and serving as the main body of the piston, a small-diameterportion (already described as the valve stem) 9 slidably insertedthrough the center bore 13 in the lower casing 7, and a connectingportion 10 b interconnecting the two portions 10 a, 9 and having adiameter intermediate between the diameters of the two portions 10 a, 9.An O-ring 17 is provided between the large-diameter portion 10 a of thepiston 10 and the upper casing 8. An O-ring 18 is provided also insidethe center through bore 13 of the lower casing 7 around thesmall-diameter portion, i.e., the valve stem, 9 of the piston 10.

A lower space S2 for the compression spring 11 to be disposed therein isformed between and defined by the lower surface of large-diameterportion 10 a of the piston 10 and the upper surface of bottom wall 7 aof the lower casing 7. The compression coil spring 11 is fitted aroundthe connecting portion 10 b of the piston 10 and has an upper endbearing against and retained by the lower surface of large-diameterportion 10 a of the piston 10 and a lower end retained by the springbearing annular recessed portion 12 of the lower casing 7. An air vent19 communicating with the lower space S2 is formed in the upper casing 8so as to be positioned a small distance above the upper end of the lowercasing 7.

In the channel opening state illustrated, the upper surface oflarge-diameter portion 10 a of the piston 10 is brought into contactwith the lower surface of top wall 8 a of the upper casing 8 by thebiasing force of the compression coil spring 11. An upper space S1serving as a compressed air admitting space is formed between anddefined by the upper surface of large-diameter portion 10 a of thepiston 10 and the lower surface of top wall 8 a of the upper casing.Compressed air for moving the piston downward is introduced into theupper space S1 through the pipe connecting internally threaded portion14 of top wall 8 a of the upper casing 8 and the downward passage 15extending from the portion 14.

FIG. 2 shows a second embodiment of fluid control device of the presentinvention. In the following description, the same components or portionsas in the first embodiment will be designated by like reference numeralsand will not be described repeatedly.

The fluid control device 21 of this embodiment is of the normally closedtype and comprises a valve case 2 provided with a fluid inlet channel 2a and a fluid outlet channel 2 b, an annular valve seat 3 formed arounda peripheral edge defining an opening of the inlet channel 2 a, adiaphragm (valve element) 4 movable into or out of pressing contact withthe valve seat 3 for closing or opening the fluid channel 2 a, a disk(vale element holder) 5 movable upward or downward for holding thediaphragm 4, a bonnet 6 fitted around the disk 5, a lower casing 7provided on an upper portion of the valve case 2, an upper casing 8joined to the lower casing 7, a valve stem 29 disposed within a spacedefined by the upper and lower casings 7, 8 and having a lower end inbearing contact with the valve element holder 5, a piston 30 secured tothe valve stem 29, and a compression coil spring 31 for biasing thepiston 10 downward.

The valve stem 29 is formed integrally with the piston 30 so as to be aportion projecting downward from the center of the piston 30. The piston30 comprises a large-diameter portion 30 a slidably fitted in the lowercasing 7 and serving as the main body of the piston, a lowersmall-diameter portion (already described as the valve stem) 29 slidablyinserted through a center through bore 13 in the lower casing 7, anupper small-diameter portion 30 b slidably fitted in a compressed airadmitting downward passage 15 in a top wall 8 a of the upper casing 8,and a connecting portion 30 c interconnecting the upper andsmall-diameter portion 30 b and the large-diameter portions 30 a andhaving a diameter intermediate between the diameters of the two portions30 a, 30 b. A spring bearing annular recessed portion 32 is formed inthe upper surface of the large-diameter portion 30 a so as to be opposedto a spring bearing annular recessed portion 16 formed in the top wall 8a of the upper casing 8.

With this embodiment, an upper space S3 formed between and defined bythe upper surface of the large-diameter portion 30 a of the piston 30and the upper surface of top wall 8 a of the upper casing 8 serves as aspace for the compressed coil spring 13 to be provided in. A lower spaceS4 formed between and defined by the lower surface of large-diameterportion 30 a of the piston 30 and the upper surface of bottom wall 7 aof the lower casing 7 serves as a compressed air admitting space. An airvent 19 communicating with the upper space S3 is formed in the uppercasing 8 so as to be positioned a small distance above the upper end ofthe lower casing 7. This air vent 19 is formed at the same position asthe one communicating with the lower space S2 in the first embodiment.This makes it possible to use the upper casing 8 in common for thenormally open type and the normally closed type although the spaces S2and S3 are different in function.

An O-ring 17 is provided between the large-diameter portion 30 a of thepiston 30 and the lower casing 7. An O-ring 18 is provided also betweenthe lower small-diameter portion, i.e., the valve stem, 29 of the piston30 and the peripheral surface of the lower casing 7 defining the centerthrough bore 13. An O-ring 33 is further interposed between the uppersmall-diameter portion 30 b of the piston 30 and the inner peripheralsurface of the upper casing 8 defining the compressed air admittingdownward passage 15, whereby the compressed air introduced into thedownward passage 15 is prevented from flowing into the upper space S3.

The compression coil spring 31 is fitted around the connecting portion30 c of the piston 30 and has a lower end retained in the annularrecessed portion 32 formed in the upper surface of large-diameterportion 30 a of the piston 30 and an upper end retained in the annularrecessed portion 16 in the upper casing 8.

The piston 30 is provided with a compressed air passageway 34 having anupper end in communication with the downward passage 15 in the top wall8 a of the upper casing 8 and a lower end in communication with thelower space S4. The passageway 34 extends through the uppersmall-diameter portion 30 b, connecting portion 30 c and large-diameterportion 30 a of the piston 30 axially thereof, and this axial passagewayportion has a lower end positioned within the lower small-diameterportion, i.e., the valve stem, 29, A radial passageway portion 34 aextends from the passageway portion lower end through the lowersmall-diameter portion 29 radially thereof, whereby the passageway 34 iscaused to communicate with the lower space S4. The compressed air formoving the piston 30 upward is introduced into a compressed airadmitting pipe connecting internally threaded portion 14 of top wall 8 aof the upper casing and the downward passage 15 extending from theportion 14, and admitted into the lower space S2 via the passageway 34and the radial passageway portion 34 a at the lower end thereof.

INDUSTRIAL APPLICABILITY

The present invention provides a fluid control device which is of thenormally open type or normally closed type as determined in accordancewith the direction of the biasing force of a spring incorporated thereinand wherein a fluid channel is opened or closed by the supply ordischarge of compressed air. The two fluid control devices of thenormally closed type and the normally open type can be reduced in thecombined number of components.

1. A fluid control device comprising a valve case having a fluidchannel, a valve element holder upwardly or downwardly movable forholding a valve element for opening or closing the fluid channel, alower casing provided on an upper portion of the valve case, an uppercasing joined to the lower casing, a valve stem disposed in a spacedefined by the upper and lower casings and having a lower end in bearingcontact with the valve element holder and a piston secured to the valvestem, an upper space being formed between and defined by an uppersurface of the piston and a lower surface of a top wall of the uppercasing, a lower space being formed between and defined by a lowersurface of the piston and an upper surface of a bottom wall of the lowercasing, the fluid control device being characterized in that acompression coil spring is provided in one of the upper space and thelower space for biasing the piston, a compressed air admittingpassageway being in communication with the other of the upper and lowerspaces.
 2. A fluid control device according to claim 1 wherein the valvestem and the piston are integral.
 3. A fluid control device according toclaim 1 or 2 wherein a spring bearing annular recessed portion is formedin each of the top wall lower surface of the upper casing and the bottomwall upper surface of the lower casing.
 4. A fluid control deviceaccording to claim 3 wherein the top wall of the upper casing isprovided with an internally threaded portion having an upward openingfor connecting a compressed air admitting pipe and a compressed airadmitting downward passage opened to the upper space and extending froma lower end of the internally threaded portion.
 5. A fluid controldevice according to claim 4 which is of the normally open type-andwherein the compression coil spring is retained by the lower surface ofthe piston and the annular recessed portion in the lower casing uppersurface.
 6. A fluid control device according to claim 4 which is of thenormally closed type and wherein a spring bearing annular recessedportion is formed in the upper surface of the piston, and thecompression coil spring is retained by the annular recessed portion ofthe piston and the annular recessed portion in the upper casing lowersurface, the piston having an upper small-diameter portion fitted in thedownward passage of the upper casing, the piston being provided with acompressed air passageway communicating at an upper end thereof with thedownward passage in the top wall of the upper casing and at a lower endthereof with the lower space.